Abutment Tooth and Base Movement With Attachment Retained Removable Partial Dentures

264 J. Dent. 1988; 16: 264-268

Abutment tooth and base movement with attachment retained removable partial dentures

G. M. Feingold, A. A. Grant and W. Johnson Department of Prosthetic Dentistry, University Dental Hospital of Manchester

KEY WORDS: Partial dentures, Precision attachments, Function

J. Dent 1988; 16: 264-268 (Received 10 Februan/ 1988; reviewed 10 March 1988; accepted 20 June 1988)

ABSTRACT Using a laboratory model for the distal extension removable partial denture situation, the effect of resilient and rigid precision attachment retainers on abutment tooth and denture base movement was studied. It was found that both abutment tooth and denture base movement was least with the rigid and semi-precision attachments used compared to the resilient attachments. Abutment tooth movement was generally towards the mesial, except for the C and L attachment which produced distal movement.

INTRODUCTION One of the accepted philosophies concerning the planning and construction of the distal extension removable partial denture is the use of stress-breaking devices as a means of distributing the load between the abutment teeth and the tissues underlying the base (Steffel, 195 1). The need for stress breakers has been suggested because the vertical displacement of the abutment tooth in its socket is approximately 0.1 mm whereas that of the mucosa underlying the base ranges between O-4 mm and 2 mm (Steiger and Boitel, 1959). This tissue resilience differen- tial of between 4 and 20 times the axial displacement of the abutment tooth is generally regarded as indicating the need for some form of stress breaking (Mensor, 1968) in order to minimize damage to the tissues during function.

The purpose of this study was to compare, using a photographic method, the effect of resilient and rigid precision and semi-precision attachment retainers on abutment tooth and denture base movement in the distal extension removable partial denture situation.

In experiments with various types of retainers using models and strain gauges, Shohet (1969) compared the stress they produced on the abutment teeth. He found that precision attachments produced the greatest degree of distal stress on single abutments and that a semi-precision

attachment, the C and L, caused less abutment tooth displacement and stress than the precision attachments.

Both Takanshi (1972) and Nally (1973) found that a rigid precision attachment produced greater loads on abutment teeth than did resilient attachments. Nally also reported that the stress produced by a rigid attachment was greater than that produced by a well-designed clasp unit. Denture base movement was greater with resilient attachments, while abutment tooth movement was little affected.

Experimenting on models with deep rest preparations and precision intracoronal rests, Cecconi (1974) found that they both influenced abutment tooth movement in the same manner. When the rests were at maximum depth, abutment tooth movement was significantly reduced. The effect of two types of stress-breaker on abutment tooth movement and denture base movement was compared by Cecconi et al. (1975) using models. Their results showed that using the Pin Dalbo attachment, denture base movement was significantly decreased when the stress- breaker was made rigid and that abutment tooth movement was significantly decreased when the Ticonium hidden lock was made rigid.

Photoelastic stress analysis was used by White ( 1978) in experiments using a Dalbo and a Mays attachment. The resilient Dalbo attachment produced identical stress

0 1988 Butterworth L Co Publishers Ltd. 0300-5712/88/06026&05 $03.00

Feingold et al.: Attachment retained removable partial dentures 265

patterns to that of the Mays attachment and resulted in the greatest stress-breaking action. When the Dalbo was deactivated, i.e. made rigid, stress on the ridge was reduced, but none of the attachments tested resulted in a wide distribution of stresses along the edentulous ridge.

Using the same experimental method, Kratochvil et al. (198 1) compared the stress distribution using the Dalbo MK extracoronal attachment, the Stemgold type 7 intracoronal attachment and the Thompson intracoronal semi-precision retainer. They reported that all attachments produced distal forces on the teeth and suggested that splinted abutments were indicated. The Dalbo MK attachment produced most force on the edentulous ridge and least force on the abutment teeth.

MATERIALS AND METHODS

An acrylic resin model of a lowerjaw was produced which incorporated a brass replica of a second premolar tooth. A silicone material, Arbrosil 188 (Adshead Ratcliffe and Co. Ltd, Belper, Derby, UK), 0.33 mm thick, was cured between the root and the socket representing the perie dontal membrane. The surface of the model was covered with the silicone material at a thickness of 2 mm in the premolar region, increasing to 3 mm in the molar area and 4 mm in the retromolar area. The upper surface of the silicone material covering the crest of the ridge descended from the distal gingival margin of the abutment tooth for 3 mm at an angle of 38 to the baseline. It then sloped upwards for 23 mm towards the distal at an angle of 9 to the horizontal, and then ascended for 5 mm at the retromolar pad at an angle of 54. A metal denture base with prepared attachment areas was cast to fit the residual ridge.

In the first experiment a Dalbo unilateral extracoronal attachment was used. The design of the Dalbo attachment is based on the Roach system allowing movement to occur in the vertical plane but not laterally.

In function, the attachment permits hinge action and vertical movement and a combination of these basic actions (Mensor, 1968). Two methods were used to alter the functional resilience of the attachment. The first of these was the removal of the stainless-steel spring. The second involved drilling a O-5 mm hole through the attachment. A 0.5 mm hard steel pin could then be passed through the hole. This prevented both the hinge movement and the vertical descent of the ball-shaped appendix, rendering the attachment rigid in nature.

The base of the model was rigidly fixed to the frame of the apparatus. Long indicator rods and pointers were fixed to the denture base and crown, and loading of the denture saddle was achieved by a static loading method at a predetermined site on the saddle (Fig. I). For the experiments reported here, a load of 10.5 4 kg was applied 20 mm from the abutment tooth. Movement of the free end of the rods magnified movement of the denture base and crowns which was measured using a photographic

Fig. 1. Model with indicator rods attached to the denture base and abutment tooth crown. The apparatus for loading the saddle is shown in position on the left side of the model.

method. This involved double exposure of a film frame- one exposure being obtained before loading and one afterwards, as described in a previous communication (Feingold et al., 1986). Two single lens reflex cameras were used, one to observe movement as seen from the anterior aspect of the model representing buccolingual movement, and another to observe the model from the lateral aspect to determine anteroposterior movement (Fig. 2).

The effect of the Dalbo attachment when used in a rigid state using the locking pin was first observed. Next, the locking pin was removed and the experiment repeated. The stainless-steel spring was then placed in position and the experiment repeated with the attachment in its normal resilient mode. Each experiment was repeated 10 times.

Further experiments were carried out using a Crismani rigid intracoronal attachment; a Crismani unilateral resilient attachment and a C and L semi-precision attachment. The Crismani rigid intracoronal attachment is basically a simple dovetailed slot device. The Crismani unilateral resilient attachment is also of a dovetail slot

Fig. 2. Diagram to illustrate the arrangement of two cameras set at right angles, to view the anteroposterior and bucce lingual movement of the indicator rods.

266 J. Dent. 1988; 16: No. 6

Table I. Movement of abutment tooth and denture base when using a Dalbo attachment in different modes

Lateral view photograph Anterior view photograph Abutment tooth Base movement

Type of attachment movement mean Direction of mean results Direction of Direction of to abutment tooth results (mm) movement (mm) tooth movement base movement

Rigid Dalbo fixed 2.52 Mesial

2.96 with pin (0.04) (O-08)

Lingual Lingual

Dalbo without spring

Dalbo with spring

3.14 (O-06)

3.23 (O-05 1)

Mesial

Mesial

3.64 (0.081)

3.1 1 (0.04)

Lingual

Lingual

Lingual

Lingual

Figures in parentheses are standard deviations.

Tab/e I/. Movement of abutment tooth and denture base using Crismani attachments in rigid and resilient modes



Crismani slide (rigid)

Crismani slide (resilient)

1.02 (0.06)

3.78 (0.05 1)

Mesial

Mesial

2.31 (O-09)

3.76 (O-1 3)

Lingual

Lingual

Lingual

Lingual


design, but having a spring-loaded platform extending horizontally over the saddle area-it is capable of permitting hinge movement, vertical translation and slight rotation in the coronal plane because of the slight taper of the dovetail section (Ray, 1969).

The C and L attachment consists of two parts: a conventionally produced spring clip which provides additional retention to a prefabricated mesially placed occlusal rest which fits into a casting having a prepared parallel-sided rest seat of dovetail form (Preiskel, 1979). This semi-precision device allows tissuewards rotation of the saddle to occur when a force is applied. All experiments were repeated 10 times.

Transfer jig for loading experiments using precision attachments

It was necessary to make a new crown for each of the precision attachments used in the experiments and a jig was constructed to ensure that the abutment tooth movement indicator rods and pointers were exactly the same length for all the experiments and to enable the crown retention screw hole and the threaded hole in the buccal cusp of the crown to be in the same relative position for all the crowns.

RESULTS

The results obtained using the Dalbo attachments (Tubk I) show that least tooth movement occurred with the

attachment in a rigid mode. The crown of the abutment tooth moved in a mesial direction. Table II also indicates less tooth movement using the rigid Crismani intracoronal attachment than that which occurred with the Crismani unilateral resilient attachment, and that abutment tooth movement was again in a mesial direction.

Tooth movement resulting from the use of the C and L attachment was less than that of either the rigid Crismani or the rigid Dalbo device, and with this attachment the movement of the abutment tooth was in a distal direction (Table III).

Measurements in each of the tables are in millimetres in the magnified dimensions as measured from the pointers. The actual tooth and denture base determined by the application of factors.

DISCUSSION

movement may be suitable correction

In this study, using the Dalbo and Crismani attachments in a rigid state, the magnitude of abutment tooth movement was significantly reduced when compared to the precision attachments in a resilient state. This is in agreement with the study of Cecconi et al. (1975), but is contrary to the results of the studies carried out by Shohet (1969), Nally (1973) and Takanshi (1972) who found that rigid precision attachments produce greater abutment tooth movement than resilient attachments.

Using the resilient precision attachments, Nally (1973)

Feingold et al.: Attachment retained removable partial dentures 267

Table /IL Movement of abutment tooth and denture base when using the C and L attachment



C and L o-57 (O-07) Distal

2.39 (O-09)

Lingual Lingual


found only average abutment tooth movement and that denture base movement was greatly increased. The experimental results are in agreement with those of Nally (1973) concerning denture base movement, but differ in regard to abutment tooth movement. They show a significant increase in denture base movement and abutment tooth movement with the Crismani resilient precision attachment (P < O-001).

Using rigid precision attachments Cecconi et al. (1975) found that denture base movement was significantly reduced, while White (1978) found a marked reduction in stress on the ridge. This study is in agreement with the results of Cecconi.

In the present studies, when the locking pin was removed from the Dalbo attachment and the spring placed in position, changing the attachment from a rigid to a resilient state, there was a highly significant increase in abutment tooth movement and significant increase in denture base movement (P < O-001 and P < O-005 respectively). When the spring was removed producing an unrestrained Dalbo, no significant change in abutment tooth movement took place, but there was a significant increase in denture base movement (P < O*OOOS). White (1978) found that when the Dalbo was progressively changed from a rigid inactive state to a more active state, at first using the spring and then without the spring, the stresses on the ridge increased and there was stress directly below the root apex of the abutment tooth, confirming reduced abutment tooth movement.

Shohet (1969) found that the greatest amount of distal stress of the abutment tooth was produced by an intracoronal rigid precision attachment and that the C and L attachment did not produce any distal displacement or stress to the abutment tooth. This study is in agreement with Shohet (1969) with regard to the small amount of abutment tooth movement, but not with regard to intracoronal precision attachments. When comparing the C and L attachment to the rigid Crismani attachment, abutment tooth movement was significantly greater for the Crismani attachment (P < O-002) but there was no significant difference in denture base movement between the two systems. However, the direction of the abutment tooth movement was distally and it was the only system using this experimental model that produced distal abutment tooth movement. This is not in agreement with Goodman and Goodman (1963) who stated that the equipoise principle of the design of the C and L

attachment produced a mesial abutment tooth movement.

If the hypothesis of Christadou et al. (1973) derived from the result of in vivo observations is correct, &e resultant of a vertical force applied to an angular ridge produces a mesially directed force to the denture base and to the abutment tooth. Then, if the abutment tooth moves even a small distance distally, it would imply that the distal force of the C and L attachment must have cancelled out the mesially directed force.

If it is considered that the best retainer design is one that produces the least abutment tooth and denture base movement, then the C and L attachment and the rigid Crismani attachment are the retainers of choice of those tested. This is shown graphically in Fig. 3 where denture base and abutment tooth movement are related for various retainer systems.

Duncans new multiple range test on the order of ranking of the five retainer systems shown indicates least denture base movement for the Crismani rigid and the C and L attachments. The same test for abutment tooth movement indicates least effect from the rigid Crismani attachment.

4

t

4 . 2 * 00 ..T i.: . 0 :?

01 I 1 I I I 0 1 2 3 4 5

Abutment tooth movement (mm)

Fig. 3. The relationship between denture base and abutment tooth movement for various retainer systems. 1, Dalbo resilient attachment; 2, Dalbo attachment with spring removed; 3, Crismani rigid attachment: 4, Crismani resilient attachment; 5, C and L attachment.

268 J. Dent. 1988; 16: No. 6

CONCLUSIONS

1. In general, the use of rigid precision attachments as retainers for the distal extension removable partial denture reduces both abutment tooth movement and denture base movement compared to that resulting from the use of resilient attachments.

2. The Crismani slide attachment and the C and L semi-precision attachment produced the least abutment tooth and denture base movement.

3. The direction of abutment tooth movement was generally mesially except for the C and L attachment which produces distal abutment tooth movement.

Acknowledgement

The apparatus used in this study was produced by Mr H. Todd, dental instructor, to whom grateful acknowledgement is made.

References Cecconi B. T. (1974) Effect of rest design on transmission of

forces to abutment teeth. J. Prosthet. Dent. 32, 14 l-l 5 1. Cecconi B. T., Kaiser G. and Rahe A. (1975) Stressbreakers

and the removable denture. J. Prosthet. Dent. 34, 145-151.

Christadou L., Osborne J. and Chamberlain J. B. (1973) The effect of partial denture design on the mobility of abutment teeth. Br. Dent. J. 135, 9-18.

Feingold G. M., Grant A. A. and Johnson W. (1986) The effect of partial denture design on abutment tooth and saddle movement. J. Oral Rehabil. 13, 549-557.

Goodman J. J. and Goodman H. W. (1963) Balance of force in precision free-end restorations. J. Prosthet. Dent. 13, 302-308.

Kratochvil F. J., Thompson W. D. and Caputo A. A. (1981) Photoelastic analysis of stress patterns on teeth and bone with attachment retainers for removable partial dentures. J. Prosthet. Dent. 46, 21-28.

Mensor M. C. (1968) The rationale of resilient hinge-action stressbreakers. J. Prosthet. Dent. 20, 204-215.

Nally J. N. (1973) Methods of handling abutment teeth in Class I partial dentures. J. Prosthet. Dent. 30, 561-566.

Preiskel H. W. (1979) Precision Attachments in Dentistry, 3rd edn. London, Kimpton.

Ray G. E. (1969) Precision Attachments. Bristol, Wright. Shohet H. (1969) Relative magnitude of stress on abutment

teeth with different retainers. J. Prosthet. Dent. 21, 267-282.

Steffel V. L. (195 1) Fundamental principles of partial denture design. J. Am. Dent. Assoc. 42, 534-544.

Steiger A. A. and Boitel R. H. (1959) Precision work for partial dentures. Stebo Zurich Switzerland Berichthaus 143-144, 157-205.

Takanshi S. (1972) Experimental studies of stress-breaking mechanisms in some kind of precision attachment applied to free-end saddle dentures. J. Tokyo Dent. Coil. Sot. 12, g&138.

White J. T. (1978) Visualisation of stress and strain related to removable partial denture abutments. J. Prosthet. Dent. 40, 143-151.

Correspondence should be addressed to: Professor A. A. Grant, University Dental Hospital of Manchester, Department of Prosthetic Dentistry, Higher Cambridge Street, Manchester Ml5 6FH, UK.

Book Review

Oral Radiology: Principles and Interpretation, 2nd edition. Paul W. Goaz and Stuart C. White. Pp. 791. 1987. St Louis, C. V. Mosby. Hardback, f38.00.

In the 5 years since its initial publication, this has become the most frequently recommended dental radiology textbook in US dental schools. Its popularity is well justified and says much about its excellence and suitability as a teaching aid. The new edition consists of 30 chapters, 20 of which have been revised, four others re-written and a new chapter on endodontic radiology added: as a result it now has 87 more pages and 162 additional illustrations.

The book is divided into seven sections, the first of which is a highly interesting historical account of the development of dental radiology and radiography, illustrated with examples of some of the early dental X-ray machines and equipment. Sections 2. 3 and 4 give accounts of the physics, the biological effects, and the safety and protection aspects of radiation. These have been updated and it is to be welcomed that measurements of radiation are now given in SI units.

Section 5 is concerned with imaging principles and includes a perspicuous description of latent image formation and an improved chapter on quality assurance, a subject which does not receive much attention in textbooks from this country. Section 6 describes intraoral and extraoral radiographic techniques and principles, including some specialised radiographic techniques, and the last section provides a comprehensive illustrated account of disorders affecting the maxillofacial region.

It is a book which is hard to fault and errors appear to be few: in figure 12.26 illustrations 8 and C are transposed and I am uncertain whether the arrows in the two illustrations in figure 15.8 point to the same area of calcification. The quality of the reproduction of the radiographs is generally satisfactory and the text easy to read and understand. It is a book which I can thoroughly recommend not only for dental undergraduates and for those studying for their Fellowship but also as a reference book for the general dental practitioner. It certainly seems to have impressed Professor Roentgen sufficiently to turn his head! (compare figure 1 .l in both editions). P. J. G. Rout

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Abutment Tooth and Base Movement With Attachment Retained Removable Partial Dentures